Hydraulic control mechanism



A. MAAS HYDRAULIC CONTROL MECHANISM Filed Nov. 27, 1957 2 Sheets-Sheet 1 Tui-biwe lhveswtmm Arno Ma. 5,

H15 Accovneg.

Turbine April4, 1939.

Driven from Turbhfie Shaft.

Shaft.

Drive-n from Turbi'r'm April 4; 1939. A, MAAS 2,153,381

HYDRAULIC CONTROL MECHANI SM Filed Nov. 27, 1937 2 Sheets-Shet 2 Drive-n from Turbine Shaft.

Inventor: A-r-1no| M as, by

His Attorn e54.

Patented Apr. 4, 1939 'UNETED STATES PATENT. OFFICE 2,153,381 HYDRAULIC CONTROL MECHANISM Arnold Maas, Berlin-Tegel, Germany, assignor to General Electric Company, a corporation of New York 7 Claims. (Cl. 121-42) The present invention relates to hydraulic control mechanismsand more specifically to the type of mechanisms for remotely controlling. a prime mover or like engine .by means including a speed governor or other controlling element responsive to changes of a condition of the engine which speed governor or element is arranged at a; considerable distance from the controlled element.

Heretofore it has been difficult accurately to con- 10, trol the valves of turbines or like elements by means of hydraulic remote control mechanisms due to inaccuracies caused by changes of the viscositypf the operating medium such as oil which made it impossible toattain a linear response between the stroke of a power piston and the change in speed or like condition.

The general object of my invention is to provide an improved construction and arrangement of hydraulic remote control mechanisms whereby accurate control is attained and the amount of operating fluid for the mechanism is considerably reduced.

For a consideration of what I believe to be novel and my invention, attention is directed to the 25 following description and the claims appended thereto in connection with the accompanying drawings.

In the drawings, Fig. 1 illustrates a hydraulic remote control mechanism embodying my inven- 30 tion, and Figs. 2 and 3 illustrate modifications of my invention. 7

The arrangement ofFlg. 1 comprises an elastic fluid turbine I!) with a'controlled element, in the present instance an inlet valve l I, for controlling the admission of elastic fluid thereto. The control mechanism for moving the valve ll comprises a controlling element, in the present instance a speed governor l2, located at a considerable distance from the inlet or admission valve H and a hydraulic motor i3 with a piston l4 secured to a stem ll which latter forms in substance an extension of the stem of the admission valve II. The supply and discharge o'f o'perating fluid to and from the motor I3 is controlled by a pilot valve l8 which has valve heads l9,aninlet conduit 20 and drain conduits 2| and 22. The vvalve headsl9 are secured to a stem 23 which in turn is pivotally connected to an intermediate point of a floating lever 24 pivotally connected at its right-,

50 hand end to the piston stem ll. Movement of the speed governor i2 is transmitted to the floating lever 24 by means includingtwo hydraulic cylinders, acylinder-l25 disposed near the governor I2 and a cylinder 26 disposed near the lever 24 and 55 connected to the cylinder 25 by conduits 21 and 28.

The cylinder 26 contains a power piston 29 secured to a stem 30 which at its lower end is pivotally connected to the left-hand end oi. the floating lever 24. The piston 29 is biased in upward direction by a spring 3| contained in the cylinder 26 5 and surrounding the piston stem 30. I

The cylinder 25 contains a piston 32 which is secured to the upper end of a hollow piston stem 33 and biased upwardly by a spring 34 contained in the cylinder 25 and surrounding the stem 33.

The stem 33 has lateral openings 35 forming part of a passage for operating fluid supplied to the upper portion of the cylinder through an inlet conduit 36 having a valve 31 and discharged from the lower portion of the cylinder through a drain conduit 38. ,The operating fluid on its path from the space above the piston 32 to the space below the piston 32 flows through the passage formed by the hollow stem 33 and the aforementioned lateral openings 35. The flowthrough said passage I is controlled by means of a suitable valve such as a needle valve 39 in cooperative relation with a valve seat formed in the upper surface of the piston 32 and secured to a stem 40 concentrically disposed within the hollow stem 33 and projecting through the lower end thereof. The stem 40 is pivotally connected to the left-hand end of a lever 4| which'has an intermediate point supported on a fulcrum 42 and a right-hand end connected to the speed governor |2.,

With this arrangement a change in speed of the turbine to-be controlled causes movement of the speed governor which in turn positions the valve 39. This changes the restriction or passage 43 formed between the latter and its valve seat. 35 More specifically, an increase in turbine speed causes outward movement of the fly weights of the governor i2 whereby the righthand end of the lever ii is moved downward thus effecting upward or opening movement of the valve 39. This increases the passage :43 and thus reduces the restriction to flow of operating fluid from the space above the piston 32 to the space below said piston 32 resulting in a drop in pressure of the fluid contained in the upper portion of the cyli'n- 5 der 25 and also in'the upper space offthe other cylinder .26. This causes upward movement of the piston 29 bythe action of the spring 3| and a similar upward movement of the pilot valve heads l9 to permit the supply of operating fluid" from the conduit 20 to the upper space in the hydraulic motor l3 and the discharge of operating fluid from the lower space of the hydraulic motor l3 through the pilot valve drain conduit 2|. The piston l4 of the hydraulic motor I3 under such a condition is moved downward and effects closing movement of the admission valve II. This movement continues until the normal operating speed of the turbine is established. Vice versa, during a decrease in turbine speed the valve 39 is moved downward effecting similar movements of the other elements as described above, but in opposite direction to eifect opening movement of the turbine admission valve ll. 7

Whenever the valve 39 is moved downward and thus the pressure above the piston 32 is increased,

the latter is also moved downward by the increased pressure in the upper cylinder portion against the pressure of the spring 34. Thus the piston 32 always follows the movement of the valve 39 and for this reason said piston 32 may be termed a follow-up piston. The cylinder 25 with its piston 32 may be termed a pressure varyingdevice because it serves 'to vary the fluid pressure in response to changes of operating condition. The other cylinder 26 together with its piston 29 may be termed a pressure responsive device in that one of its elements, the piston 29, is moved in response to pressure changes. In these arrangements, it is oi. primary importance that the movement of thepressure responsive device is always either equal or proportional to the movement of the pressure varying device. This is accomplished in accordance with my invention by properly dimensioning the two devices 25 and 26. In the present instance, the inner diameters D1 and D2 of the cylinders 25 and 26 are alike. Likewise the outer diameter di of the piston stem 33 is equal to the outer diameter d: of the piston stem 39. e

Let us assume that the fluid pressure in the supply conduit 36 be pi which pressure is throttled down by the valve 31 to eifect a pressure m above the piston 32 in the cylinder 25. The pressure then in the space above the piston, 29 is also pa.

The pressures in the spaces below the pistons 32 and 29 are pa. Under such condition the pressure varying piston 32 is held in position as long as equilibrium exists between the force exerted by pressure p: on its upper surface and the force exerted by the pressures p: and P1 acting on the lower surface ofthepiston, the force P1 representing the compression of the spring 36. Likewise, the piston 29 remainsin position as long as balance exists between the force exerted by the pressure pa on its outer surface nd the forces egcerted. by the pressures in and 2 on its lower surface. P2 represents the compression of the spring 3 i In the present instance with the pressures p: and m alike in the two cylinders P1 must be equal to P2. In an arrangement of this kind, the strokes of the pressure varying or follow-up piston 32'and the power piston or pressure responsive piston 29 during any load change will be alike or at least proportional. In other words, the pressure curve of the fluid contained in the conduit 28 'connecting the two cylinders 25 and 26 must have a linear course. Changes of viscosity of the operating fluid then can have no disadvantageous effect on the mechanism. An arrangement of this kind, however, necessitates the circulation of a comparatively considerable amount of operating fluid such as 011 because both cylinders are of the same size and have to be filled and drained within a short period of time to permit quick opening and closing of the'turbine admis-'- sion valve.

Fig. 2 shows an arrangement in which the amount of operating fluid is considerably reduced and at the same time the periods of starting and shutting down the turbine kept at a minimum. More specifically, the arrangement includes a turbine with an admission valve 5| which is controlled by a mechanism comprising a hydraulic motor and pilot valve 52 corresponding to the hydraulic motor l3 and the pilot valve l9 of the arrangement in Fig. 1. In addition, the mechanism comprises a speed governor 53 driven from the turbine shaft and connected to a stem 54 of a needle valve 55 corresponding to the stem 49 and the valve 39 of Fig. 1 and forming a part of a pressure varying device 56. The device 56 is connected to a pressure responsive device 51 corresponding to the device 26 of Fig. 1. The arrangements of Fig. 1 and Fig. 2 are alike with the following exceptions. The device 56 is considerably smaller than the device 51 and, whereas in Fig. 1 operating fluid is directly supplied to the cylinder 25, in the arrangement of Fig. 2 the operating fluid is supplied by, a conduit 58 with the valve 59 to the device 51. The conduit 59 is connected to the inlet conduit for the hydraulic motor and pilot valve 52 whereby both the-hydraulic motor and the devices, 56 and 51 are connected to the same source of fluid under pressure. sure varying device 56 has an outlet or drain conduit 60. The inner diameter D1 of the device 56 is smaller, than the diameter D: of the device 51. Also the diameter (11 of the piston stem of the device 56 is smaller than the diameter d2 of the piston stem of device 51. In an arrangement of this kind, the strokes of the pistons of the devices 56 and 51 are no longer alike. In order, however, to maintain proportionality of movements between the two pistons, the ratio of the compressions of the springs 6| and 62 of the devices 56 and 51 respectively must meet the following condition:

fi Pf(mp:)+ 1'pa 2 (PaPt) 2 Pi The pressures pa, p: are the fluid pressures in the upper and lower space respectively of the devices 56 and 51. The formula applies to both arrangements in Figs. 1 and 2.

The operation of the mechanism of Fig. 2 is the same as that described above in connection with Fig. 1. However, while the fluid in the conduits 21 and 28 connecting the two devices in'Flg. 1 may flow in either direction, in the arrangement of Fig. 2. the flow of fluid in the conduit 63 connecting the upper spaces of the two devices'is unldirectional because in this arrangement .the operating fluid is supplied to the device 51 and not to the device 56.

The arrangement of Fig. 3 comprises a turbine The pres- 65 with an inlet valve 66 which is connected to a hydraulic motor 61 controlled by a pilotvalve 66 having stems connected to a floating lever 69 corresponding to the lever 24 of Fig. 1. Thelefthand end of the floating lever 69 is connectedto the lower end of a piston stem 19 forming part of a pressure responsive device 'll. The device H in addition includes a piston 12 secured to the upper end of the stem 19 and biased upwardly by a compression spring 13 surrounding the stem portion 19 reduced in diameter with regard to the lower portion thereof.- A pressure varying orv device located near the control element, a pressure responsive device located near and connected to the controlled element, each device comprising a cylinder, a piston with a stem movably disposed therein and a biasing spring engaging the piston, the piston and stem of the pressure varying device having equal diameters and forming a passage through which fluid is discharged from the space above said piston, and a valve cooperatively associated with the last mentioned piston and connected to the control element for controlling the flow of fluid through said passage, a conduit for conducting operating fluid under pressure to the space above one of the pistons, a conduit connecting'the spaces above the pistons, and a drain conduit connected to the space below the piston of the pressure varying device.

6. A hydraulic remote control mechanism including the combination of a control element, a controlled element, and means for transmitting movement of the control element to the controlled element, comprising a pressure varying device located near the control element, a pressure responsive device located near and connected to the controlled element, each device comprising a cylinder, apiston with a stem movably disposed therein and a biasing spring engaging the piston, the piston and stem of the pressure varying device having equal diameters and forming an a passage through which fluid is discharged from the space above said piston, and a valve cooperatively associated with the last mentioned piston and connected to the control element for controlling the fiow oi fluid through said passage, a conduit for conducting operating fluid under pressure ,to the space above one of the pistons, a

conduit connecting the spaces above the pistons,

a drain conduit connected to the space below, the piston of the pressure varying device, the two'devices being located at different levels, and means for compensating the hydrostatic pressure difference due to said different levels, comprising an adjustable plug engaging one of the springs.

7. A hydraulic remote control mechanism including the combination of a speed governor, a valve for controlling the flow of elastic fluid to an engine, means for transmitting movement of the governor to the valve comprising a first and a second cylinder each having a piston with a stem and a biasing spring for the piston, means connecting the stem of the second cylinder to the valve, conduit means directly connecting the cylinders, means for conducting fluid under pressure to one of the cylinders, means including a bore formed in the piston and the stem of the first cylinder for discharging fluid therefrom, and

a valve having a stem connected to the speed governor and located in the bore for controlling the fluid discharge. 7

ARNOLD MAAS.

follow-up piston I8 is disposed within the upper portion 18 of the cylinder 11 and connected to a hollow stem. 88. The piston 19 is biased upwardly by a compression spring 8| bearing at its upper end against a collar 82 formed on the hollow piston stem 88'. Operating fluid is supplied by a conduit 88 including a valve 84 to the upper space in the cylinder 1i whence the fluid flows through the conduit 15 into the cylinder portion II to be discharged therefrom through a passage formed by the hollow piston stem 88 and lateral openings 85 in said stem into the lower'space of the cylinder 11 which latter is connected to a drain conduit 86. The flow of fluid through the hollow piston stem 88 is controlled by a valve 81 corresponding to the valve 38 in Fig. 1 and connected to a stem 88 which latter is pivoted 'at its lower end to a fulcrumed lever 89 moved by a speed governor 80 driven from the turbine.

In this arrangement, the spaces below the pistons 12 and 18 are no longer connected by a conduit. This is made possible because the diameter D1 of the pressure varying or follow-up piston 18 is equal to the diameter d1 of the. stem connected thereto. 'The device 1! is located a distance H above the level of the device Tl. In order to compensate the pressure difference in the pressure varying and the pressure responsive devices due to their locations at different levels, an initial or additional compression is imparted to the spring of one of the devices. -In the present instance, this may be readily accomplished by properly adjusting the spring plug 14 of the pres sure responsive device H. The ratio of the biasing force of the springs 8| and 18, that is,

' is the same as expressed by the above formula if we merely consider P: the biasing force of the springs 18 after deduction of an initial force imparted to the spring to compensate for the level difference H.

Having described the method of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new anddesire to secure by Letters Patent of the United States is:

l. Hydraulic remote control mechanism cluding the combination of an element responsive to a change in operating condition of a machine to be controlled, a pressure varying device connected to the element and including a cylinder with a follow-up piston having a hollow piston stem and means connected to the element for controlling the flow of operating fluid through the hollow piston stem, at pressure responsive device having a cylinder with a piston having a stem movably disposed therein, a compression spring in each device engaging its piston, means for conducting operating fluid to one of the devices, and conduit means connecting the devices, the dimensions of said devices satisfying the following formula cluding the combination of a controlled element, a control element located at a considerable distance from the controlled element, and means for transmitting movement of the control element to the. controlled element comprising a pressure responsive device having a cylinder, a-

piston movably disposed in the cylinder, a stem secured to the piston and connected'to the controlled element' and a spring engaging the piston, a pressure varying device located near 'the control element and including a cylinder, a followup piston movably disposed therein, a hollow stem spring engaging the follow-up piston, and avalve cooperatively associated with the follow-up piston and having a stem connected to the control element, conduit means connecting the spaces formed above and below the pistons of the two -with lateral openings secured to the piston, a

conduit means connecting the two devices and supplying operating fluid under pressure thereto,

each device having a cylinder, a piston disposed in the cylinder, a stem connected to the piston anda spring engaging the piston, the pressure varying device in addition including a valve connected to the control element for controlling the flow of operating fluid from the space formed above its piston to the space formed below its piston, the springs of the two devices being dimensioned to satisfy the following formula movement of the control element to the controlled element comprising-a pressure varying device mechanically connected to the control element, a pressure responsive device connected to the controlled element, each device having 2. cylinder, a piston with a stem. movably disposed in the cylinder and a biasing spring engaging the piston, a conduit for supplying fluid under pressure to one of the devices, a drain conduit for the pressure varying devices, conduits connecting the spaces above and below the pistons respectively, the diameter of the pistons and their I stems as well as the characteristics of the biasing springs being alike.

5. A hydraulic remote control mechanism including the combination of a control element,

a controlled element,and means for transmitting movement of the control element to the controlled element, comprising a pressure varying 

